very constant air-possible?

[nerobro]

500watts. 500watthours... lets see here. Volts times amps = watts.... Say we have a 12 volt battery. You'd need a 41 amp hour battery. That's a car battery. And a good sized one at that.

a 4.5 amp hour battery is 3.6 lbs. You would need thirty six pounds of battery. and then the wireing to hook it up.....

A 41 amp hour battery would take a good 8hrs to recharge after using it for that hour.

Now a small gas engine... say a .10 ci engine could provide that kind of energy. And run on a pint of gas for.. an hour or more. (depending on how much you use the air in the system ;-) Im' sure it would throttle down as the tank completeed filling)

Heck if you didn't mind having to wait a bit longer for a fill a .061 could handle filling tasks. And that would run for twice as long as the larger engine ;-)

......... so.. yea.. batterys are a bad idea for this.

This is actually an idea I've been cooking up for a while now. My original idea was to work with centrifugal compressrors... because of the rpm these motors turn. a .049 runs at 12,000+rpm ;-)

[nerobro]

Come on, someone has to know about high pressure moving seals... :-)

[xatle]

you only need 28 psi if you wanna run it constant with no accumulation chamber, you can probably achieve this with a very small multi stage axial compresser. i doubt you would need a real high torque motor, you may even be able to run it with an electric motor thats small enough to run off its own emag battery 20+ minutes.

just some thoughts, have fun with it.

[TRIAD]

I think the most realistic idea that wouldn't require combustible fuel would be liquid nitrogen. It's about 2 bucks a pound, and they make 25 pound tanks that can be filled. That takes care of getting a massive amount. You could carry one or two pounds in a large tank, say on your back (we're talking scenario here). Then, that would connect to a smaller tank with a large surface area (the liquid is going to need to absorb a lot of energy in order to go to a gas). After that, you'd just feed the gas into the gun, and there you have it. This seems feasible for a scenario player.

Now for some calculations:

Let's say you have 1 Kg of liquid N2, that's about 2.2 pounds. Then you have about 35.696 moles of N2. Convert that to liters of gas at atmospheric pressure, you have about 800 liters. Change that to 800 psi, you have about 14.7 liters of 800 psi gas. Let's change that to 4500 psi to see what size compressed air tank you'd need for that much, and you get about 2.61 liters. So, 2.2 pounds of liquid N2 is the equivalent of a 2.6 liter 4500 psi compressed air tank, as far as moles of gas (and number of shots). The advantages of storing the substance as a liquid are obvious. Now, CO2 is also stored as a liquid, and we can see how CO2 is bad. So, I am not sure how well the N2 would boil in the "expansion chamber", but I do know that it would create the pressure necessary. So, that's what I think would be the most feasible way to power a gun for the scenario player, and maybe even the tourney play with a smaller setup.

[bjjb99]

Originally posted by xatle
you only need 28 psi if you wanna run it constant with no accumulation chamber, you can probably achieve this with a very small multi stage axial compresser.

You need to apply a constant 25-ish psig pressure throughout the paintball's acceleration down a foot-long barrel to get it to exit at 300 fps.

Remember, the lower the pressure, the higher the flow rate needs to be to compensate. The compressor would have to provide a flow of around 45 cubic feet per minute through that barrel in order to keep the pressure up near the end of the paintball's acceleration.

BJJB

[nerobro]

Good question there, but that would require a custom gun.

And keep in mind that you want that barrel near atmospheric pressure when that ballleaves, or at least in the region. not at 2 bar. Yes, axial compressors can generate that kind of pressure, fairly easily even ;-)

I think that a displacement pump would have lower energy demands in the long run....

[shinobidice]

i'm pretty sure that liquid nitrogen would freeze up anything on your gun, including the fact you couldnt use macro becuase it would freeze solid in a few tenths of a second if that. Not only that, you'd need a HUGE expansion chamber to get the liquid n2 to be warm enough not to completely kill your gun. Plus for all the cocker users, what would that do to the tiny 3 way hoses? any thoughts?

[nerobro]

shin: the idea would be to vaporize the nitrogen for use.

[J_Hoyt]

Yes, but how would you vaporize it? Like shin said, you'd need an expansion chamber. Or something to provide heat well into the dangerous range. You want to use HPA in the same way as CO2. Stored as a liquid, used as a gas. Well, there are 2 ways to liquefy nitrogen. Make it OFF-THE-CHARTS, FREAKING COLD!! or REALLY amp up the pressure.

Either drop the temperature of the tank to -190 C - meaning you'd have to heat it all up by that much before it gets to the gun - or increase the pressure. By my quick crappy calculations that may not even be close, you'd need it at about 23000-24000 PSI. But the pressure thing is obvious. If we cram more air into a tank, yes it will last longer. It doesn't necessarily have to liquefy.

What you guys want is 13000 PSI tanks, where a 15ci tank will last as long as a 45/45. Or you could play an entire tournament or scenario game with an 88 or 114.

Problem is, fills that high are impossible to get. So we'd have to drop the temperature of the tank. And there's no safe way to do that.

[Fuji]

How about using a TEC, but instead flipping it around? TECs are used quite a bit in the CPU overclocking world as a way to bring the temperature of something down. TECs have a hot plate and a cold plate. So flip it around and use the hotplate side to heat the LN2 up.

Although, to be honest LN2 doesn't require much to flash back into a gas. I'm pretty sure that with a heatsink & expansion chamber big enough you could flash the liquid into a gas way before it hits the marker. Only problem I see is that you may wind up "iceballing" the whole works as you get into high ROFs.

I also have to agree with triad. I don't think that it would be very weight/cost effective to go with a backpack/ongun motor rig for compression.

As far as low operating pressures, shockers are fairly decent. The only setback being the who gas inefficiency thing. Low pressure requires higher flow rate.

I'm thinking that at this time that if you went LN2, you would want a medium high operating pressure marker. Less flow and the LN2 can flash fairly quickly.

[xen_100]

Re: you guys kind of get

Originally posted by sharpshooter1286
what i meant was that it wouldnt store air it would just constantly feed the gun. i think it could be done if someone had it hooked up to a battery pack or a motor in their harness and the tank was filled with filters and the fan and stuff

it just wouldn't work. take those self inflating bed for example. I have one that operates off of 4"D" batteries. the batteries last about 10 fills and empties. total about 10-20 minutes of running the motor. it has a decent amount of volume to it, but no pressure. once the bed gets full the motor whines and slowes downs. this is about 5-10PSI.

you would need a fan the size of a small wind tunnel to get the kind of pressure and volume needed to power a paintballgun. size and battery requirements would be much larger than a small pack mule could carry let alone a paintball player on the field.

[nerobro]

I'd take a pressure guage to that. My bet is that you're only actually seeing 1-3psi. "A" psi is a ton of force. :-) airball bunkers are only inflated to a max of a coupple psi. Usually they are at 1 or less. :-)

it's areally all a matter of time. even a few d size batterys can generate huge pressures, but only in small volume. if you can work out the CFM the gun needs, we can work from there.

then again, we covered energy requirements earlier ;-)

[xen_100]

lol.......even better......I was being a bit genereous by saying 5-10 PSI.